Oxyluminescent panel



United States Patent 3,360,426 OXYLUMINESCENT PANEL Edward T. Cline, Wilmington, Del., assignor to E. I. du Pont de Nernours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Aug. 15, 1966, Ser. No. 572,87 4 6 Claims. (Cl. 161-196) This application is a continuation-in-part of my copending application Ser. No. 477,614, filed Aug. 5, 1965, which in turn is a continuation of my copending application Ser. No. 463,398, filed June 11, 1965; Ser. No. 463,- 398 itself being a continuation-in-part of my copending application Ser. No. 397,038, filed Sept. 16, 1964, both now abandoned.

This invention relates to improved extended light sources based on chemiluminescent materials. More particularly, the invention relates to composite articles comprising oxyluminescent panels having improved properties.

Oxyluminescent articles comprising porous substrates impregnated with tetrakis(disubstituted-amino-ethylene oxyluminescent materials enclosed in flexible, translucent plastic envelopes or tubes fitted with means for admitting air have been described and claimed in my earlier filed applications referredto above, especially US. application Ser. No. 477,614. Such composite articles (light sources) are highly usefulas safety devices in facilitating rescue of personnel lost in isolated places on land or on water. They provide a light which is visible for considerable distances and that can be activated by personnel from air craft downed at sea or 'in isolated areas on land or by ships personnel overboard at sea. While these particular devices can be stored for long periods and are ready for immediate use when the need arises, some of the embodiments, especially those having envelopes of poly(vinyl fluoride), discolor when stored under mildly elevated temperatures and theirlight output decreases with length of storage.

The present invention provides improved extended light sources of the above-described type. These exhibit improved stability atelevated temperatures, have improved strength and are provided with an improved means of introducing air to the enclosed oxyluminescent compositions to generate light from the panel.

The light source of the present invention comprises an oxyluminescent panel or envelope of the type described in my aforementioned application Ser. No. 477,614, in which the enclosing envelope or panel is (1) constructed of a particular polyamide film, viz., a transparent film of polycaprolactam, poly-(hexamethyleneadiparnide) or poly(hexamethyleneseb'acamide) enclosing the oxylumines'cent composition, (2) one surface of the polyamide panel is laminated to a sheet of aluminum foil, and (3) to the opposite transparent surface of the polyamide panel are sealed one or more narrow strips of a thicker or stronger plastic film which, when pulled, results in the thinner or weaker enclosing envelope being ruptured at or near the edges of the tear strips, whereby air is admitted to the oxyluminescent composition contained in the envelope, thereby causing the composition to luminesce.

If desired, the panels of the above-defined structure, like the panels of my earlier applications, can be provided with means, such as snaps, for attaching one or more panels to each other or to other objects to provide a larger area of light.

The oxyluminescent materials useful in the light sources of this invention are the tetrakis(di-substituted-amino)- ethylenes of the formula 3,360,426 Patented Dec. 26, 1967 wherein the Rs are the same or diiferent and are monovalent alkyl or cycloalkyl of up to 10 carbon atoms, divalent alkylene joined to the other R attached to the same nitrogen to form a 3-5 membered monoaza heterocycle, and divalent alkylene joined to an R attached to a second nitrogen to form a 3-7 membered diaza heterocycle. Specific oxyluminescent compounds of this type include tetrakis(dimethylamino)ethylene, tetrakis(N-pyrrolidinyl)ethylene, 1,1,3,3'-tetramethyl-A '-bi(imidazolidine 1, 1',3,3'-tetraethyl-A '-bi(imidazolidine) 1,1',3 3'-tetramethy1-A '-bi(hexahydropyrimidine), and tetrakis dimethyl-aminomethylene amino ethylene.

The tetrakis(dimethylamino)ethylene can be prepared by reaction of dimethylamine with chlorotrifluroethylene as described in J. Am. Chem. Soc. 72,3646 (1950). The other tetrakis(disubstituted amino) ethylenes of the above general formula and the bis(disubstituted-amino)- hydrocarbyloxymethanes intermediate thereto can be prepared by the process which is described in detail in US. Patent 3,239,519 issued to H. E. Winberg.

The oxyluminescent materials used in the panels of this invention are conveniently used with an inert, nonquenching solvent or carrier, i.e., a material which does not extinguish the oxyluminescence of the tetrakis-(disubstituted-amino)ethylene. Suitable solvents of this type include the hydrocarbons such as n-hexane, decane, decalin, trisobutylene, cetane, tetra-isobutylene n-octadecane, 1- octadecene, purified kerosenes, white gasolines, or the more viscous hydrocarbons such as mineral oil and the like, or solid or semisolid hydrocarbons such as paraffin wax; nonquenching synthetic oils such as silicone oils, polyalkylene glycols, and diesters; nonquenching, preferably essentially hydrocarbon esters such as ethyl acetate; nonquenching hydrocarbon ethers such as tetrahydrofuran, diethyl ether, dimethyl ether, and the like.

The oxyluminescent compositions can also include compatible nonquenching, organic or inorganic, thickening agents. Examples of suitable nonquenching thickening agents include nonreducible, noncoordinating inorganic oxides, preferably in colloidal dispersion, such as silica, alumina, zinc oxide, and the like; organic nonquenching polymers such as the hydrocarbon polymers, e.g., polyisobutylene, polypropylene, polyethylene, and the like; nonquenching polyesters, e.g., polyvinyl acetate and the like; nonquenching polyethers such as polytetramethylene oxide and the like; nonquenching olefin/ ester copolymers such as ethylene/vinyl acetate copolymers and the like.

As disclosed in my parent application, U.S. Ser. No. 477,614, the oxyluminescent materials of the type defined above are preferably absorbed on a porous substrate in the polyamide envelope. Useful substrates of this type for use in the articles of the present invention include foamed or otherwise cellular sheets or ribbons of polymers such as polystyrene, polyurethanes, poly(vinyl chloride), polyethylene, and polyacrylonitrile; glass fiber fabric (both Woven and nonwoven); cellulosic paper such as bleached kraft paper or sulfite paper; fabrics (both woven and nonwoven) of such fibers as poly(ethylene terephthalate) fiber, rayon, cotton, nylon and acrylic fiber; mats or fabrics made of porous poly(vinylidene chloride) fibers and vinyl chloride copolymers; sheets made of opaque, foamed plastc fibers; sheets of alkali cellulose; nonwoven sheets of polyethylene or polypropylene fibers; and glass fiber sheets, paper, and mats.

Likewise, it is preferable to position spacers between the porous substrate and the enclosing polyamide envelope to provide more intense light emission from the oxyluminescent layer as disclosed in my above-mentioned application Ser. No. 477,614. Suitable spacers can be made of any inert nonquenching material that can be fabricated in an open-mesh or net-like structure. Examples of specific spacers that are satisfactory include polyethylene netting, polypropylene netting, cheesecloth, nylon scrim, nylon netting, loosely woven glass fiber fabric, and the like. No spacer is needed with porous substrates that have a rough or uneven surface that permits good air circulation.

The polyamide films used as the enclosing envelopes and the tear strips of the articles of the present invention are made by conventional methods from the commercially available polyamides, viz., polycaprolactam, poly (hexamethyleneadipamide), and poly(hexamethylenesebacamide).

The tear strips used in the articles of this invention are conveniently made of the same polyamide as that used in the envelope but are thicker and therefore stronger in order to make sure that the envelope is torn when the strip is pulled. If desired, tear strips made of any other polymers which are stronger than the enclosing envelope and are heat scalable thereto can be used.

The aluminum foil laminated to the back side of the envelope of this invention provides increased light emission by reflection of the light from the oxyluminescent composition back through the front of the panel. Moreover, this aluminum foil backing also increases the strength of the panel. Aluminum foil of one-mil thickness gives good results, but if panels able to resist rougher handling are desired, the aluminum foil backing can be made of foil of greater thickness. Optionally, another layer of a heat sealable film can be cemented to the back of the aluminum foil if it is desired to attach the panel to an object by heat-sealing. Examples of such heat scalable backing films include polyethylene and polypropylene. An optional embodiment comprises the use, as a reflective film attached to the back of the polyamide envelope, of a plastic film having dispersed therein reflective pigments, e.g., aluminum flake pigment, preferably with the aluminum flakes oriented parallel to the surface of the film.

The oxyluminescent panels of this invention can be stored in sealed containers of metal, glass or plastic until needed. By keeping moisture and oxygen away from the panels, there will be no loss of activity despite long periods of storage.

The oxyluminescent panels of this invention are illustrated in further detail in the following examples.

Example I A panel having an active area of 4" x 6 is prepared by heat-healing three edges of two 4%" x 6%" sheets of 2-mil thick polycaprolactam film. One of the 4% edges of the panel or pouch is left unsealed. One face of the polycaprolactam panel, viz., the upper face, is provided with two tear strips, 2 /2 long and 1 wide, spaced parallel to the shorter panel dimension and 1 /2" up and down from the longer panel dimension. The tear strips are constructed of S-mil polycaprolactam film heatsealed lengthwise over a A x 1 /2 portion in the center of the strips to the upper face of the panel, with the end /2" portions unsealed, so that pulling the S-mil tear fiap causes the 2-mil film comprising the upper face to tear along the heat seal. A 4" X 6" piece of fine glass fiber paper substrate weighing approximately 1.2 g. is placed in the pouch. To serve as a spacer between the substrate and the outer envelope, 4" x 6" pieces of nylon netting are placed between both sides of the glass fiber paper and the polycaprolactam film. The fourth edge of the pouch is then heat-sealed. A hypodermic needle is inserted in the excess length to permit exhausting the air in the pouch by alternately evacuating and filling with nitrogen. By means of a hypodermic needle, the glass fiber paper is then impregnated with 6 ml. of a 50% by volume solution of tetrakis(dimethylamino)ethylene in mineral oil. The hole left by the needle is covered with tape until a heat seal is made in the polycaprolactam envelope between the hole and the porous substrate. The excess material is then cut from the pouch, and to the lower face of the panel, i.e., the face opposite that having the tear strips, is cemented a layer of l-mil aluminum foil.

In the dark, the panel is activated by pulling the loose ends of the tear flaps, thus permitting ingress of air to the oxyluminescent layer. The brightness of the resulting blue-green oxyluminescence is measured with a photometer. It is found to be 6.3 foot lamberts after one minute,, 4.6 foot lamberts after five minutes, and 2.2 foot lamberts after 10 minutes.

Examples II, III and IV Three panels are prepared as described in Example I but replacing the 50% by volume solution of tetrakis(dimethylamino)ethylene in mineral oil with one of the following oxyluminescent compositions for each panel: (1) 4 ml. of tetrakis(dirnethylamino)ethylene; (2) 6 ml. of a mixture of 7.5 parts of tetrakis-(dimethylamino)- ethylene; 2.5 parts of l,1',3,3-tetraethyl-A '-bi(imidazolidine) and 10 parts of mineral oil; (3 6 ml. of a mixture of 2.5 parts of tetrakis(dimethylamino)ethylene, 2.5 parts of decane, and 0108 part of decyl alcohol.

The light emission produced after pulling the tear strips to activate the oxyluminescent compositions in the panels, as measured by a photometer, is given in the following table:

Brightness, in Foot Lamberts, After- Example 1 min. 5 mins. 10 mins. 15 mins. 30 mins.

1. (3 0. 75 0.20 0.05 Dark 0. 46 O. 33 0.23 0. 18 0. l1 1. 3 0. 0. 55 O. 19 0. 07

Examples V and VI Two panels are prepared as described in Example I but replacing the polycaprolactam envelope with (l) 2-mil poly(hexamethyleneadipamide) film and (2) 2-mil poly(hexamethylenesebacamide) film. The tear flaps are constructed of S-mil polycaprolactam film 1 /2 long and /2" wide (with about /2 of one end left unsealed), heat-sealed to the 2-mil poly(hexamethyleneadipamide) film in. the first panel and to the 2-rnil poly(hexamethylenesebacamide) film in the second panel. The porous layer of each panel is impregnated with 6 m1. of 50% by volume solution of tetrakis(dimethylamino)ethylene in mineral oil. On activating the panels by pulling the tear flaps in a darkened room to admit air, the panels luminesce brightly.

Example VIl Panels are prepared by the method described in Example I with 2-mil polycaprolactam envelopes, glass fiber paper substrates and nylon netting spacers, and have an active area of 12" x 18" and an over-all dimension of 14 /2 x 20 /2. The porous layer is impregnated with 55 ml. of a composition comprising equal volumes of tetrakis (dimethylarnino)ethylene and mineral oil. To one face of the polycaprolactam envelope is cemented a layer of aluminum foil; then a 2-mil commercial vinyl film known as Contact is cemented to the aluminum foil. The opposite, upper face of the envelope is provided with two 4" tear strips symmetrically spaced parallel to the 12 panel dimension and one-third of the way up and down the 18" panel dimension. The tear flaps are constructed of S-mil polycaprolactam film heat-sealed to the 2-mil polycaprolactam upper face so that pulling the S-rnil tear flap causes the 2-mil film to tear along the Wide heat seal, thus permitting ingress of air to the oxyluminescent layer.

At night, the panels are activated by pulling the tear flaps. The resulting blue-green oxyluminescence from a single panel is visible even in a horizontal position at about two miles slant range and altitudes of 1000 and 2000 feet.

Example VIII The superiority of the polyamide envelopes used in the oxyluminescent articles of this invention compared to one of the better envelope materials previously employed is shown by this example.

An open-end pouch is made by heat-sealing three edges of two 4% x 6%" sheets of 2-mil thick polycaprolactam film. One of the 4% edges of the pouch is left unsealed. A 4" x 6" piece of fine glass fiber paper substrate weighing approximately 1.2 g. is placed in the pouch. To serve as a spacer between the substrate and the outer envelope, 4" x 6" pieces of nylon netting are placed between both sides of the glass fiber paper and the polycaprolactam film. The fourth edge of the pouch is then heat-sealed. A hypodermic needle is inserted in the excess length to permit exhausting the air the pouch by alternately evacuating and filling with nitrogen. By means of a hypodermic needle the glass fiber paper is then impregnated with 6 ml. of a 37% by volume solution of tetrakis(dimethylamino)ethylene in mineral oil. The hole left by the needle is covered with tape until a heat seal is made in the polycaprolactam envelope between the hole and the porous substrate. The excess material is then cut from the pouch. Similar panels are made using Z-mil films of poly(hexamethyleneadipamide), poly(hexamethy1enesebacamide) and an oriented poly(viny1 fluoride) in place of the polycaprolactam.

The panels are stored at 160 F. in a circulating air oven. Within two days the poly (vinyl fluoride) panel is grossly discolored and the light output decreases rapidly with length of storage. In contrast, the panels based on polyamide envelopes are only moderately discolored after up to three weeks at 160 F. and the light output remains good.

As indicated previously, the extended light sources of this invention are useful in many applications. More particularly, the oxyluminescent panels are highly suitable for aiding in the rescue of crew members and passengers of aircraft which have been downed at remote, uninhabited places on land or sea. The panels are especially suitable for the emergency lighting of life rafts, life vests and various locations in the interior of aircraft. The flexibility of the panels enables emergency equipment to which they are attached to be folded up for storage until needed in emergency. The oxyluminescent articles carried by the aircraft in an inactive state can be activated rapidly when needed to signal rescuers at night.

The foregoing detailed description has been given for clarity of understanding only and no unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described for obvious modifications will be apparent to those skilled in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An oxyluminescent panel comprising an enclosure of polyamide film containing a porous substrate impregnated with a tetrakis(disubstituted-amino)ethylene oxyluminescent material, said panel having one surface laminated to a sheet of aluminum foil and the opposite transparent surface of the panel sealed toat least one tear strip of a stronger plastic film, which, when pulled, causes the weaker enclosing polyamide envelope to be ruptured at or near the edges of the tear strip, thereby admitting air to the oxyluminescent material and causing it to lum-inesce.

2. Panels of claim 1 wherein the oxyluminescent material is a tetrakis(disubstituted-amino)ethylene of the formula wherein the Rs, which need not be the same, are selected from the group consisting of m-onovalent alky'l of up to 10 carbons, monovalent cycloalkyl of up to 10 carbons, divalent alkylene joined to the other R attached to the same nitrogen to form a 3-5 membered monoaza heterocycle, and divalent alkylene joined to an -R attached to a second nitrogen to form a 3-7 membered diaza heterocycle.

3. Panels of claim 2 wherein the oxyluminescent material is in an inert carrier.

4. An oxyluminescent panel of claim 1 wherein the porous substrate is impregnated with tetrakis(dirnethylamino) ethylene.

5. An oxyluminescent panel of claim 1 wherein the polyamide film is selected from the class consisting of polycaprolactam, poly(hexamethyleneadipamide) and poly (hexamethylenseb acamide) 6. An oxyluminescent panel of claim 1 wherein the substrate is glass fiber paper and is impregnated with tetrakis (dimethylamino)ethylene enclosed in a transparent envelope of polycaprolactam film, said substrate being kept out of intimate contact with the enclosing envelope by means of a spacer of nylon netting.

References Cited UNITED STATES PATENTS L. DEWAYNE RUTLEDGE, Primary Examiner. 

1. AN OXYLUMINESCENT PANEL COMPRISING AN ENCLOSURE OF POLYAMIDE FILM CONTAINING A POROUS SUBSTRATE IMPREGNATED WITH A TETRAKIS(DISUBSTITUTED-AMINO) ETHYLENE OXYLUMINESCENT MATERIAL, SAID PANEL HAVING ONE SURFACE LAMINATED TO A SHEET OF ALUMINUM FOIL AND THE OPPOSITE TRANSPARENT SURFACE OF THE PANEL SEALED TO AT LEAST ONE TEAR STRIP OF A STRONGER PLASTIC FILM, WHICH, WHEN PULLED, CAUSES THE WEAKER ENCLOSING POLYAMIDE ENVELOPE TO BE RUPTURED AT OR NEAR THE EDGES OF THE TEAR STRIP, THEREBY ADMITTING AIR TO THE OXYLUMINESCENT MATERIAL AND CAUSING IT TO LUMINESCE.
 6. AN OXYLUMINESCENT PANEL OF CLAIM 1 WHEREIN THE SUBSTRATE IS GLASS FIBER PAPER AND IS IMPREGNATED WITH TETRAKIS(DIMETHYLAMINO)ETHYLENE ENCLOSED IN A TRANSPARENT ENVELOPE OF POLYCARPROLACTAM FILM, SAID SUBSTRATE BEING KEPT OUT INTIMATE CONTACT WITH THE ENCLOSING ENVELOPE BY MEANS OF A SPACER OF NYLON NETTING. 